1. Field of Disclosure
This disclosure relates to an optical sensing device, and more particularly to an optical sensing device of which the adjacent reading lines are coupled to the optical sensing units with different characteristic value.
2. Related Art
Please refer to FIG. 1, which illustrates a schematic diagram of the conventional optical sensing module. The optical sensing module 100 comprises an optical sensing unit 102, a reading unit 104, and a charge storage unit 106. The optical sensing unit 102 is connected to a control line 107 with a predetermined voltage level Vg, such as 5V. The reading unit 104 is connected to the reading line 108 for outputting a readout voltage Vout. The other terminal of the optical sensing unit 102 is connected to a scanning signal with a predetermined voltage level Vs. The reading unit 104 is connected to another control line 112 with the predetermined voltage level Vg. The charge storage unit 106 is electrically coupled to the optical sensing unit 102 and the reading unit 104. The reading unit 104 is enabled before the optical sensing unit 102 is enabled. In other words, before the control line 107 enables the optical sensing unit 102, the control line 112 enables the reading unit 104.
While the optical sensing unit 102 is enabled, a capacitor C in the charge storage unit 106 is recharged so that the capacitor C has a cross voltage Va. The capacitor C is connected to a DC voltage. When the optical sensing unit is exposed to light, the cross voltage Va is decreased owing to the current leakage according to the strength of light. The voltage level of the cross voltage of the capacitor C is read out to the reading line 108 when the reading unit 104 is enabled. The reading line 108 is connected to a reading circuit which is not shown in FIG. 1, and the reading circuit determines the strength of light received by the optical sensing module 100 according to the voltage level of the cross voltage of the capacitor C read by the reading unit 104.
The optical sensing module 100 may comprise a plurality of aforementioned optical sensing units 102, and each optical sensing unit corresponds to one aforementioned reading line 108. Because the light received by the optical sensing module may be received by more than one optical sensing unit, more than one reading line 108 will reflect a variation of voltage of the capacitor C. Hence, the reading lines 108 of the optical sensing module are connected to a differential amplifier so as to determine a region receiving the light. As above, because more than one optical sensing unit 102 receives the light, a method for increasing the sensitivity of the optical sensing module 100 for determining the region receiving the light is a topic to be solved in this disclosure.